A slow leak inside a wall can rot the wood post that holds up a beam. Once you see it, you want two answers fast: is the house safe, and what will this cost?
Here is a real one we priced in 2026: one rotted post under a beam in a Park City lower-level bedroom. We priced it two ways, so you can see what the structural work costs on its own and what it costs to make the room look finished again.
The problem
One 6x6 wood post under a glulam beam in a lower-level bedroom. A plumbing leak had rotted it.
Post work only
$14,194, fixed price, about one week on site.
Post plus closing the wall
$28,954, with insulation, drywall, trim and paint. About two weeks on site.
Not in either price
Structural engineering (the owner hired it), permit and inspection fees (billed at cost) and the plumbing repair.
Priced
September 2026, in Park City.
What was wrong
A plumbing leak inside a bedroom wall had soaked the base of a 6x6 post for a long time. That post holds up a glulam beam, and the beam carries the floor above.
The owner did the right things before calling us. He opened the wall, had the leak fixed, let everything dry out, and hired a structural engineer. Nobody touched the post until the engineer's stamped plans said exactly what should replace it.
How a post gets replaced
- Protect the room. Floors and the path in and out get covered before work starts.
- Shore the beam. Steel screw jacks go in on both sides and take the load off the old post.
- Take out the old post. The rotted post and any damaged material come out and get hauled off.
- Set the new post. It goes in with the size, base and top connections the engineer's plans call for.
- Inspect. The city inspects the new post and connections before the jacks come out.
- Clean up. Then either close the wall or leave it open, depending on the scope.
Where the money went
The structural work itself was the smaller half of the job. Closing the wall and making the room look new again doubled the price.
| Scope | Price | Time on site |
|---|---|---|
| Post only: protect, shore, replace the post, haul off, clean, supervise | $14,194 | About 1 week |
| Post plus insulation, drywall patch, baseboard and a full room repaint | $28,954 | About 2 weeks |
Both were fixed prices in September 2026. Permit and inspection fees were billed at cost in both. The finish work and the extra week of supervision account for the difference of about $14,800.
What changes the number
- The engineer's plans. Our price assumed one post swapped like for like with standard hardware. A new footing, a beam repair or added framing would be priced separately.
- The beam. If the beam above the post is damaged too, it has to be repaired or replaced, and that costs more than the post.
- Hidden damage. Once the old post is out, more rot can show up. Work should stop for a written change order before anything else is done.
- Pipes and wires in the way. Water lines or wiring in the same bay add time.
- Closing the wall. Insulation, drywall, trim and paint can cost as much as the structural work.
If you find a rotted post
- Stop the water first. A new post in a wet wall will rot too.
- Do not jack, cut or remove anything yourself. The post is carrying weight.
- Hire a structural engineer before you ask for prices. Every contractor should price the same stamped plans.
- Leave the wall open until it is dry. Take photos every few weeks.
- Get a fixed price that lists what is included and what is not, in plain words.
How we handle it
We price structural repairs from the engineer's stamped plans, as one fixed number with the exclusions written out. A project manager runs the job every day it is open, and the shoring stays in until the inspector signs off.
Common questions
How much does it cost to replace a structural post?+
For one water-damaged 6x6 post under a beam in a Park City home, our 2026 fixed price was $14,194 for the post work only. With the wall insulated, drywalled, trimmed and painted again, it was $28,954. Engineering and permit fees were extra in both.
Do I need a structural engineer to replace a post?+
Yes. A post holds up a beam, and the beam holds up the floor or roof above it. The engineer says what size post goes in and how it connects at the top and bottom. Our price waited on the engineer's stamped plans.
How long does it take to replace a post?+
About one week on site once the stamped plans and the permit are in hand. Closing the wall back up added about another week.
Is the house safe while the post is out?+
Yes, if it is shored first. Steel screw jacks carry the beam before the old post comes out, and they stay until the new post and its connections pass inspection.
Can the wall be left open after the repair?+
Yes. This owner asked us to leave the wall open through the winter so he could watch the cavity for any new water. Closing it became a separate, later price.
What if there is more damage behind the post?+
Work stops and you get a written change order before anything else is done. A rotted footing, a damaged beam or extra framing are the most common surprises.
Where these numbers come from
The numbers come from Three Peak's fixed-price proposal for a Park City home in September 2026. Every repair is different, so your engineer's plans and your estimate set your real number.
Keep reading
Next Step
Found a rotted post or a sagging beam?
Send us photos and your engineer's plans if you have them. We will tell you what the repair involves and what to budget.
Schedule a ConsultationOr call 435-214-1669